Challenging to meet 1nm iso-dense bias (IDB) by controlling laser spectrum

According to the ITRS Roadmap, for 45nm Node (as 65nm Half Pitch), the requirement of Gate CD Control is defined as 2.6nm. One of the most challenging CD errors is Iso-Dense Bias (IDB). Assuming 40% of CD errors are dominated by IDB, IDB should be less than 1nm. In general, the majority of IDB is due to: primarily, exposure tool- related factors such as aberrations, flare, and sigma fluctuation, and secondly, the change in photoresist characteristics. However, due to the rapidly increasing usage of ArF exposure tools, Band Width (BW) characteristics of the laser source is an additional factor whose contribution is becoming more critical. Ideally, BW is monochromatic, thereby not affected by chromatic aberration change. However, in reality, the BW exhibits a shape of spectral distribution with a finite width. This study describes experimental and simulation results for E95%, and how performance of both CDs and Laser is dependent on E95% in order to meet 1nm of IDB towards 45nm Node. -IDB vs. E95% -CD at through pitch vs. E95% -Process Latitude vs. E95% -DOF -EL -Pattern shortening vs. E95%